1. Some information about the walkie-talkie launch:
The RF carrier signal emitted by the phase-locked loop and the voltage-controlled oscillator is amplified by buffering, which encourages expansion, power amplifier, and additional RF power. It passes through the antenna low-pass filter, presses the harmonic component, and then transmits it through the antenna.
2. Accept some:
Some of the two-frequency super-heterodyne methods are accepted. The signal input from the antenna is amplified by the transceiving conversion circuit and the band-pass filter, and then amplified by the band-pass filter to enter a mixing frequency. The top-end local oscillator signal of the phase-locked loop frequency synthesizer circuit is mixed at the top mixer and generates the top IF signal. The top frequency IF signal further eliminates the adjacent channel clutter signal through the crystal filter. The filtered top frequency intermediate frequency signal enters the intermediate frequency processing chip, and the second local oscillation signal is mixed again to generate a second intermediate frequency signal, and the second intermediate frequency signal is filtered and removed by a ceramic filter, and then amplified and frequency-divided. audio signal. The audio signal is expanded into a bandpass filter, de-emphasized, etc., and the volume control circuit and the power amplifier are expanded to drive the speaker to obtain the information that everyone needs.
3. Modulation signal and modulation circuit:
The human voice is converted into an audio electrical signal through a microphone, and the audio signal is directly modulated by the expansion circuit, the pre-emphasis circuit, and the band pass filter into the voltage controlled oscillator.
4. Signaling processing:
The CTCSS/DTCSS signal generated by the CPU is adjusted and expanded to enter the voltage controlled oscillator for modulation. The low-frequency signal obtained after receiving the frequency discrimination is filtered and shaped by the bandpass filter of the sub-audio, and enters the CPU to compare with the preset value, and the result is to control the output of the audio power amplifier and the speaker. That is, if it is the same as the preset value, the speaker is turned over, and if it is not the same, the speaker is closed.
5, the walkie-talkie has a frequency limit:
In order to ensure that most users are not disturbed and use frequency resources reasonably, the National Wireless Desk handles the use of frequency, and the industry with different rules uses the corresponding frequency scale. When purchasing a walkie-talkie, users should apply to the local radio handling committee for frequency.
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